Heavy-ion collisions and QCD in PHENIX at RHIC

1. Heavy-ion collisions and QCD in PHENIX at RHIC ByungsikHong Korea University STAR Asia & Heavy-Ion Meeting

2. Contents • Introduction-Skip • PHENIX detector-Future upgrade plan • Recent Results • Initial state effects • Cold nuclear matter & gluon saturation • p+p vs. d+Au • Elementary p+p data • Serve as the reference for A+A • Final state effects • Effects of bulk matter • p+p vs. d+Au vs. A+A • Summary STAR Asia & Heavy-Ion Meeting

3. PHENIX status & plan • Recent detector improvements • Large & more accurate reaction-plane detector (RXNP) • Higher-pTPID (TOF-West) • Forward calorimeters (MPC) • Hadronblind detector (HBD) • Future upgrade plan • Muon trigger system for high-pTmuons (decayed from W’s) • (Korean Participation: Korea University & Hanyang University) • Si-vertextrackers for accurate secondary vtx measurements • Si-W forward calorimeters to enlarge the acceptance of g & h • (Korean Particiaption: Chonbuk Nat. U., EwhaWomans U., • Korea U., Myongji U., Yonsei U. from Korea) • Continuing DAQ upgrades to maintain high speed and efficiency STAR Asia & Heavy-Ion Meeting

4. RPC1 RPC3 RPC3 PHENIX upgrade plan Forward Si-W Calorimeter (FOCAL, formerly NCC) STAR Asia & Heavy-Ion Meeting

5. Initial State Effect STAR Asia & Heavy-Ion Meeting

6. CNM & gluon saturation High-gluon density ⇒ Nonlinear g-g fusion pQCD factorization should be broken K.J. Eskola et al., arXiv:0902.4154 Nonlinear Linear RGPb(x, Q2=1.69 GeV2) Non-perturbative • Gluon saturation is expected to be amplified in nucleus. • Initial state energy loss & multiple scattering Evolution in Q2 by DGLAP: Evolution in x by BFKL: STAR Asia & Heavy-Ion Meeting

7. Rapidity-separated hadron correlations in d+Au: Yields Trigger π0 or h± π0 d Au y<0 y>0 IdAuissuppressed at forward rapidity for more central collisions. STAR Asia & Heavy-Ion Meeting

8. Rapidity-separated hadron correlations in d+Au: Widths No large broadening of the correlation peak with centrality within uncertainties STAR Asia & Heavy-Ion Meeting

9. Mid-rapidity jet pairs • Number of jet pairs scales faster than Ncoll(near side shown, far side similar) • Large Cronin-like enhancement • Jet shapes: no centrality dependence STAR Asia & Heavy-Ion Meeting

10. Initial state with photons Isospin, Cronin, shadowing, dE/dx Vitev, nucl-th/0810.3194v1 (all data: PHENIX preliminary) Photons in Au+Au have some modification at high pT, but may be just due to the CNM effects – i.e. Cronin & Isospin effects STAR Asia & Heavy-Ion Meeting

11. Initial state with photons arXiv:0804.4168v1 [nucl-ex] • Fit to the pT slope in central collisions: • Tavg= 221±23±18 MeV • Expansion models • Tavg= 221 Tinit > 300 MeV Large enhancement above the scaled p+pspectra in low-pT “thermal” region STAR Asia & Heavy-Ion Meeting

12. Elementary p+pCollisions STAR Asia & Heavy-Ion Meeting

13. Quark contribution to high-pTnonphotonic electrons • Up to 16% decrease in open heavy for pT> 5 GeV/c • Similar story for Au+Au, and RAuAuis not much changed. STAR Asia & Heavy-Ion Meeting

14. Open heavy quarks arXiv:0903.4851 [hep-ex] STAR Asia & Heavy-Ion Meeting

15. Open heavy quarks • Substantial fraction of b→efor large pT • b cross section consistent with FONLL STAR Asia & Heavy-Ion Meeting

16. e-mcorrelations • Opposite sign e- pairs with ≈  • Product of back-to-back charm pairsproduced mainly via gluon fusion • Pure signal • Few sources of physics background • No contribution from Drell-Yan, thermal production, and resonance decays • Like-sign subtraction removes combinatorial background⇒ e- pairs from dijets e- pair Invariant Yield=2.11*10-7±3.4*10-8(stat)±3.5*10-8(sys) STAR Asia & Heavy-Ion Meeting

17. Quarkonium: J/y’s • 2006 p+pdata: ~3 times previous (2005) luminosity! • Much improved baseline, especially for high pT STAR Asia & Heavy-Ion Meeting

18. J/y polarization • New color singlet model (CSM), fitted to the CDF data • agrees with the data at mid-rapidity. • fails(at 2~3 s level) to explain the forward rapidity data. Haberzettl, Lansberg PRL 100, 032006 (2008) STAR Asia & Heavy-Ion Meeting

19. Quarkonium: ’s • Cross section follows the world trend. • Baseline for Au+Au STAR Asia & Heavy-Ion Meeting

20. Final State Effect STAR Asia & Heavy-Ion Meeting

21. suppression in AA Au+Au [8.5,11.5] nunlike=17 & nlike=5 p+p [8.5,11.5] nunlike=12 & nlike=1 STAR Asia & Heavy-Ion Meeting

22.  suppression in AA with RAA (J/y) = 0.425±0.025±0.072 from PRL 98, 232301 (2007) • RAuAu[8.5,11.5] < 0.64 at 90% C.L. whatever the source (, open b, DY) is. • What can cause the  suppression? STAR Asia & Heavy-Ion Meeting

23. Nuclear modification STAR Asia & Heavy-Ion Meeting

24. Similar RAAfor equivalent <Npart> • Already seen for p0, but RAA(f) ≠ RAA(p0) RAA of f in Cu+Cu STAR Asia & Heavy-Ion Meeting

25. RAA of heavy flavor Single m± at Forward Rapidity Single e± at Mid-Rapidity • Stronger suppression at the forward region than at mid-rapidity? • It agrees with the trend already seen for J/y. STAR Asia & Heavy-Ion Meeting

26. Azimuthal dependence pT RAA In-plane Intermediate Out-of-plane NPart • Out-of plane RAA nearly flat with centrality at low pT • In- and out-of-plane converge at high-pT≥ 10 GeV/c STAR Asia & Heavy-Ion Meeting

27. Di-hadron correlations Near side: Df~ 0 Near-side features: Ridge (Dh) Away side: Df~ pAway-side features: Head & Shoulder STAR Asia & Heavy-Ion Meeting

28. RP dependent correlations Analyzed in 18 |ftrig- y| angle bins of 5o in 0~90 degrees STAR Asia & Heavy-Ion Meeting

29. Head Shoulder In detail • Head: yield confirms a simple picture of energy loss vs. path length • Shoulder: hard to disentangle the geometry effects STAR Asia & Heavy-Ion Meeting

30. inclusive photonic HF e-h correlations Heavy flavor per-trigger yield p+p: 2.0<pT,e<3.0 GeV/c STAR Asia & Heavy-Ion Meeting

31. HF e-h correlations in pp STAR Asia & Heavy-Ion Meeting

32. Now in Au+Au PHENIX PRELIMINARY An interesting first look and proof of principle. Need more data. STAR Asia & Heavy-Ion Meeting

33. Direct g-jet correlation g g (q) g (q) g (q) jet associated hadrons • g*→e+e-/μ+μ- • is also possible • g is not affected by strong interaction • no surface bias ⇒ probe the entire geometry • well calibrated: Eg ~ Ejet • How is the energy loss distributed in the jet fragmentation cone? STAR Asia & Heavy-Ion Meeting

34. arXiv:0903.3399 Head region Direct g-jet correlation Away-side suppression in Au+Au STAR Asia & Heavy-Ion Meeting

35. Jet fragmentation func. • Slope comparison • p+p: 6.890.64 • - Au+Au: 9.491.37 Jet fragmentation function is modified in Au+Au. STAR Asia & Heavy-Ion Meeting

36. Flow-v2 • KET/nq scaling for baryons and mesons agree at low pT(< 1 GeV). • KET/nqscaling suggests that the flow has been established at the partonic level. STAR Asia & Heavy-Ion Meeting

37. PHENIX Preliminary PHENIX Preliminary Flow-higher order • Scaling works for v4as well as for v2 • v4= k(v2)2, independent of particle species • The flowdata can be used to test hydrodynamical models • & extract the transport coefficients. STAR Asia & Heavy-Ion Meeting

38. Summary • Hints of CNM in d+Au collisions • Rapidity-separated hadron correlations • RAA of direct photons • More elementary p+p data • Nonphotonic high-pT electrons • Fraction of b in high-pTnonphotonic electrons • More accurate J/y data • First J/y polarization &  production • Numerous evidence for FSI • Systematiccomparison of single particle RAA • Azimuthal dependence of RAAw.r.t. the RP • Di-hadron correlations w.r.t. the RP: peculiar development of head & shoulder components as a function of the centrality • HF e-m correlation • Directg-jet correlation: modification of the jet fragmentation function • Number of constituent quark scaling of v2 & v4 STAR Asia & Heavy-Ion Meeting